Thromboses prophylaxis

Drugs that decrease the coagulability of blood, such as coumarins andhep-arin (A), are employed for the prophylaxis of thromboses. In addition, attempts are directed at inhibiting the aggregation of blood platelets, which are prominently involved in intra-arterial thrombogenesis (p. 148). For the therapy of thrombosis, drugs are used that dissolve the fibrin meshwork->fibrino-lytics (p. 146). 

First, the protocol may induce the detection of extra cases - cases that would have gone undetected if no protocol were used in the usual care of patients. These cases may be detected earlier than they would have been in usual care. In the prophylaxis example above, repeated testing of all patients is likely to increase the number of deep vein thromboses that are detected, especially if, in usual care, patients are only tested when they develop clinical signs of deep vein thromboses. This extra or early detection may also reduce the average costs for each case detected, because subclinical cases or those detected early may be less costly to treat than clinically detected cases. However, because these two potential biases - more cases, each of which may cost less -work in opposite directions, the total costs of care for patients in the trial may or may not exceed those that would occur in usual care. 

Heparin is administered intravenously or subcutaneously. The maximal anticoagulant effect is obtained within a few minutes after intravenous injection, 2-3 hours after slow intravenous infusion and within 2—4 hours after subcutaneous injection. The indications are the prophylaxis and treatment of thromboses and embolism of the lungs. 

Henry Howell (1860-1945) and is extracted nowadays from the mucous membranes in the small intestine of pigs, or from the lungs of cattle. The drug inhibits the transformation of fibrinogen into fibrin, and is now used for the treatment of thromboses, embolisms and for the prophylaxis of cardiac infarction and thrombosis. A disadvantage is, that heparin is not resorbed from the gastrointestinal tract, and has to be administered via an intravenous, subcutaneous or percutaneous route. 

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